John of Brienne

John of Brienne (1170-27 March 1237) was the Latin Emperor jointly with Baldwin of Courtenay from 1229 to 1237, succeeding and preceding Baldwin. From 1210 to 1225, he was also King of Jerusalem, succeeding Maria of Montferrat and preceding Isabella II of Jerusalem.

Biography
John of Brienne was born in 1170, the youngest son of Erard II of Brienne, a wealthy nobleman from Champagne, France. When his brother Walter III of Brienne died in 1205, John became the regent of the County of Brienne for his infant nephew Walter IV of Brienne, who lived in Italy. With the consent of King Philip II of France and Pope Innocent III, he headed to the Holy Land and married Queen Maria of Montferrat of the Kingdom of Jerusalem, becoming jure uxoris King of Jerusalem and regent for their child Isabella II of Jerusalem after Maria's death in childbirth in 1212. John was one of the leaders of the Fifth Crusade in Egypt, and 1219 he was recognized as the lord of Damietta. When he remarried to Stephanie of Armenia, he claimed the Armenian Kingdom of Cilicia for himself, but the recapture of Damietta by the Ayyubids in 1221 led to the end of the Fifth Crusade, so he married his daughter off to Frederick II of Germany in 1225 to gain European assistance in the Holy Land. Frederick ended John's rule in Jerusalem, and the popes failed in persuading Frederick to recognize John as the official king. John was granted the ability to administer papal domains in Tuscany, and in 1228-1229 he led papal forces against Frederick during the war between the Holy Roman Empire and Papal States. In 1229, he was elected Latin Emperor with Baldwin of Courtenay, but Ivan Asen II of Bulgaria and John III of Nicaea conquered Thrace from John, and he held off Nicene and Bulgarian forces in a siege of Constantinople from 1235 to 1236. He became a monk of the Dominican Order afterwards, and he died in 1237.